Electrical control system



June 5, 1945. s. H. PARDEY ET 2,377,365

ELECTRICAL common SYSTEM Filed A ril 8, 1945 INVENTORS Patented June 5,1945 ELECTRICAL CONTROL SYSTEM George H. Pardey and Cornelius L.Johnson. Cleveland, Ohio, assignors to The Motor Repair andManufacturing Company, a corporation of Ohio Application April 8, 1943,Serial No. 482,333

10 Claims.

Our invention relates in general to electrical control systems and moreparticularly to an electrical control system for controlling anintermittent drive. i

In this application we are illustrating the use of our invention asbeing applied to control the traverse of a tool device Withreference toa re clprocal work table upon which the work piece is mounted that is tobe cut by the tool. Although we are showing theme of our invention asbeing applied to the machine tool as described, it is to be understoodthat our invention may be applied to other machinery having intermittentdriving operations.

An object of our inventionis to provide for intermittently energizing amagnetic clutch which interconnects a driving shaft and a driven'shaft,whereby the driven shaft is operated through substantially apredetermined number of revolutions.

Another object of our invention is the provision of an electrical timingcircuit which governs the duration during which the magnetic clutch isenergized to transmit power from one shaft to another.

Another object of our invention is the provision of energizing themagnetic clutch for a predetermined length of time which governs theamount that the driven shaft is turned.

Another object of our invention is the provision of intermittentlyoperating a driven shaft, wherein the intermittent operation is governedby an electrical timing circuit which may be adjubted to vary theduration of each intermittent operation. v

Another object of our invention is to provide for intermittentlyoperating a tool device with reference to a reciprocal work table, inwhich the movement. of the tool device is governed by an electricaltiming circuit which is set into operation in'accor'danc'e with thereciprocal movements of the work table.

Another object of our invention is the provision of operating or movingthe tool device with reference' to the reciprocal work table during theinterval or substantially at thesame time that the reciprocal work,table is being reversed.

Another object of our invention is to provide for electricallyenergizing the intermittent drive for the movement of the tool devicesubstantially simultaneously at the same time that the electricalcircuits are established for reversing the drive of the reciprocal worktable. I O

Another object of our invention is to provide for using the trippingarrangement which reverses the direction of the drive for the reciprocalwork table for also controlling the initiation of the electrical timingcircuit which governs the amount of energization supplied to theelectrical intermittent drive which moves the tool device with referenceto the reciprocal work table.

Another object of our invention is to provide for arresting the movementof the tool device with reference to the reciprocal work table in theevent that the electrical timing circuit fails to operate.

Other objects and a fuller understanding of our invention may be had byreferring to the following description and claims, taken in conjunctionwith the accompanying drawing, in which the figure represents adiagrammatic illustration of a control system embodying the features ofour invention.

As hereinbefore mentioned, our invention is shown as being applied to areciprocal work table identified by the reference character H! which maybe suitably driven by a drive and control unit indicated by thereference character ll. As diagrammatically illustrated, the drive andcontrol unit may be operated in one direction by manually depressing thepush button 2| and may be manually operated in the reverse direction bydepressing the push button 22. Any suitable means may be employed toreciprocally operate the work table In and as illustrated we employ rackand pinion arrangement I2 and I3. The movement of the reciprocal worktable to the right is designated as the forward direction and themovement of the reciprocal work table to the left isdesignated asthereverse direction. When the reciprocal work table II] reaches the end ofits forward movement, a projection 69 engages a toggle arrangement 6!which functions to close the contacts H and I2. The closure of thecontacts ll establishes a circuit through conductor 18 for reversing thedrive and control unit H to re ciprocate the work table It) in thereverse direction. The work table moves in the reverse direction untilthe projection 10 engages the toggle arrangement 68 which operates toclose the contacts l3 and 14. The closure of the contacts 13 establishesa circuit through conductor 19 for reversing the operation of the driveand control unit II to reciprocate the Work table In in the forwarddirection. As the projections 69 and 10 pass back underneath theirrespective toggle arrangements, the operation is such that the con-'tacts controlled thereby are restored to their open" I position asillustrated in the drawing. The toggle respect to each other so that theprojections 89 and I only engage their respective toggles. The showingand the operation of the reciprocal movements of the work table by thedrive and control unit I I is abbreviated and condensed for the reasonthat this constitutes no portion of our invention, except only that ourinvention is associated with the particular diagrammatic arrangement asillustrated.

The tool device is illustrated by the reference character I4 and isarranged to be moved laterally with respect to the work table as eachcut is made upon the work piece. As diagrammatically illustrated, thetool device may be moved in a transverse arrangement with respect to thework table by means of a screw traverse assembly I5 which may be drivenby an electric motor I1 through means of an electric magnetic clutch I8and reducing speed gears I 6. An electric brake I9 is associated withthe magnetic clutch so that when the magnetic clutch is energized totransmit power the electric brake I9 is released through theenergization of the brake windings 20.

The electric motor I! may be energized from a suitable alternatingcurrent supply indicated by the reference character 25. The starting andstopping of the electric motor Il may be accomplished by a relay 29having contacts 30 and the direction of rotation of the electric motorII may be controlled by the reversing control unit 26 which when thepush button 21 is depressed operates the motor in one direction and whenthe push button 28 is depressed the motor operates in the reversedirection. The motor I! is continuously driven and the magnetic clutchI8 is operated intermittently to intermittently move the tool device I 4with reference to the reciprocal work table upon actuation of the togglearrangement 81 or 68 depending upon the direction of travel of thereciprocal work table and upon whether the transfer switch I5 isengaging contact 84 or 85. The duration through which the magneticclutch is energized is governed by an electrical timing circuitindicated generally by the reference character 3B which comprises a gridcontrolled rectifying tube 31, a condenser 48, an adjustable resistor49, a fixed resistor 5|, and the secondary windings 33, 34 and 35 of atransformer 32 which in turn is energized by a transformer 31 connectedto the alternating current supply 25. The grid controlled rectifyingtube comprises a heated cathode 38, a plate 39 and a control grid 40.The cathode 38 is heated by the secondary winding 35 of the transformer32. The plate circuit of the rectifying tube is energized by thesecondary winding 34 and may be traced from the left-hand terminal ofthe secondary winding 34 through conductor 45 to the cathode 38, theplate 39, a conductor 45 to the winding of a relay 44 and through aconductor 4'! to the opposite terminal of the secondary winding 34. Whenthe tube 81 is conducting current the relay 44 is energized and closesthe contacts 52, 54 and 55 and opens the contacts 58 and 53. The closureof the con.- tact 52 connects the secondary winding 33 in electricalcircuit connection with the condenser 48 which electrically charges thecondenser 48 preparatory to discharging same through the adjust ableresistor 49 upon the reclosure of the contact 58 which connects theadjustable resistor 49 in closed circuit relation with the condenser 48.During the discharging of the condenser 48 through the adjustableresistor 49, the tube 3! becomes non-conducting until the condenser hasbeen discharged to a predetermined condition,

after which it again becomes conducting to resume the cycle ofoperation.

The operation of the complete circuit arrange-- ment may be described asfollows: assuming that the work table III is moving to the right asshown in the drawing, and that the rectifying tube 31 is conducting, inwhich event the relays 44 and 58 are energized, the motor I! may then bestarted by depressing the start push button 42 which establishes acircuit for energizing the re" lay 29 for closing the contacts 30 whichconnect the motor l1 to the alternating current supply conductor 25. Therelay 29 when once energized by depressing the push button 42 iscontinuoush energized through the contacts 4| which are closed when therelay is once energized. Consequently, the motor II continues to runeven though the contacts 55 of the relay 44 are open and even though thestart push button 42 is open. The rectifying tube 31 continues to beconducting and the relay 44 continues to be energized until theprojection 69 engages the toggle arrangement SIat which time thecontacts II and 12 are closed. Th closure of the contacts II providesfor reversing the direction of the drive and control unit for reversingthe movement of the reciprocal work table III to the left. The closureof the contacts I2 establishes a circuit for energizing therelay 65which circuit extends from the direct current supply conductor 80, thewinding of the relay 85, a conductor IS, the contacts I2. a conductor I1and a transfer switch I5 to the pposite side 54 of the supply source.The energization of the relay 65 opens the contact 678 for disconnectingthe condenser 48 from circuit relation with the secondary transformerwinding 33 Interruption of the circuit by the opening of the contact 86causes the condenser 48 to affect the control grid 48 such that the tube31 becomes non-conducting at which point the relay 44 is deenergized.The de-energization of the relay 44 closes the contact 53 whichestablishes a circuit for energizing the magnetic clutch I8 and thewindings 20 of the brake I9. The circuit for energizing the magneticclutch I8 and the brake winding 20 may be traced as follows: beginningwith the direct current supply conductor 50. current flows throughconductor 88, the contacts 53, conductor 8|, the magnetic clutch I8 andthe brake winding 20, and conductor 82 to the op posite side of thedirect current supply source 64. The relay 44 remains de-energized forsupplying current to the magnetic clutch for a short interval of time asdetermined by the rate at which the condenser 48 is discharged throughthe adjustable resistor 49 which is connected in closed circuit relationwith the condenser 48 through the closed contacts 50. As previouslyexplained. when the condenser 48 is discharged to a predeterminedcondition the tube 31 again becomes conducting at which point the relay44 is again;

energized which interrupts the circuit for supplying the current to themagnetic clutch. Durin the interval that the magnetic clutch isenergized,

the motor [1 drives the gears I6 and the screw traverse assembly l5 formoving the tool device I4 a small distance with reference to thereciprocal work table for taking another cut upon the Acccrddevice asmall distance, upon the projection 69 pp the toggle arrangement 61. Themovement of the tool I4 is substantially concurrent.

with the tripping of the toggle arrangement so that the projection 69need not move much lieyond the toggle arrangement for effecting theproper movement of the tool H. The operation the toggle arrangement 61.Upon the transfer of the switch 15 to the opposite contact 85, themovement of the tool I4 is eifected when the projection 10 engages thetoggle arrangement 68/ When the toggle arrangement 61 or 68 as the casemay be are restored to their normal position upon the reversal of thework table, the relay 65 is again de-energized which closes the relaycontacts 66 for re-establishing the timing circuit by connecting thesecondary transformer winding 33 in circuit relation with the condenser48 and the fixed resistor through the closed contacts 52 for againrecharging the condenser 48 preparatory to another cyclic operation. Thetube 31 remains conducting and the relay 44 remains cnergized until therelay 65 is again re-energized for interrupting the contact 66. Consequently, the relay 44 remains energized throughout the period that themovable work table travels before the projection 59 or 10, as the casemight be, engages the respective. toggle arrange ment, and momentarilyremains deenergized during the time that the electrical timing circuit36 causes the tube 31 to be non-conductive.

Accordingly, in our control system the magnetic clutch is energizedmomentarily through the closure of the contacts 53 during the periodthat the relay 44 is de-energizcd which is determined by the dischargingof the condenser 48 through the adjustable resistor 49. The distancethat the tool I4 is moved may be accordingly varied by adjusting theadjustable resistor 49 which varies the discharge rate of the condenser48. In the event that the tube should fail forany other reason so thatthe relay 44 remains de-energized for too long a period, we provide fortie-energizing the motor l1 through means of a relay 58 which isenergized through a circuit including the con tacts 54 of the relay 44.The circuit for energizing the relay 58 may be traced from the directcurrent supply conductor 60 through conductor iii, the adjustableresistor 62, the winding of the relay 58, and the contact 54 to theopposite side of the direct current supply source 64. The condensor 63is connected in parallel with the adjustable resistor 52 and the winding58 which tends to hold the relay 58 energized for a redetermined lengthof time after the contacts 54 are open upon the de-energization of therelay 44. Thus, the relay 58 is set for a longer period of time than thesetting of the electrical timing circuit 36 so that in the ordinaryoperation of the electrical timing circuit 36 the relay 58 alwaysremains closed. However, in the event that the relay 44 remains open fora longer period of time than that de tcrmined by the discharge of thecondenser 48, such for example, as upon the failure of the tube 31, therelay 58 becomes de-energized and opens the contacts 59 for energizingthe relay 29 which disconnects the motor [1 from the alternating currentsupply 25. The relay 58 may thus be characterised as a safety relay toprevent the motor" from driving the tool H in the event of failure ofthe electrical timing circuit 36. A push button is connected in parallelwith the contacts 53 so that upon depressingthe push button 83 themagnetic clutch I8 may be energized separately from the electrical timincircuit for continuously moving the tool M. The push button 83 may beused for setting the tool 14 for the initial settingoperation.

We find fromactual experience that the arrangement provides forgivingvery accurate control over the movements of the tool device I4 withreference to the reciprocal work table and that the movement of the toolwith respect to the workpiece is substantially concurrent with thetipping of thetoggle arrangement for reversing the direction of themovement of the reciprocal work table. The entire system for operatingthe tool device maybe arrested by olepressing the stop button 43.

Although we have described our invention with. a certain degree ofparticularity, it is understood that the present disclosure has beenmade only by way of example and that numerous changes in the details ofconstruction and the combination and arrangement of parts may beresorted to Without departing. from the spirit and the scope of theinvention as hereinafter claimed.

We claim as our invention:

1. In a control system having a driving shaft, a driven shaft, amagneticclutch between the two shafts, and a source of electrical current, theimprovement of circuit means for. momentarily energizing the magneticclutch for transmitting power from the driving shaft to'the drivenshaft, said improvement comprising circuit connection means forconnecting the magnetic clutch to the sourc of electric current, and anelectrical timing circuit including a grid-controlled tube and acapacitor for governing the circuit connection means.

Z. In a control system having a driving shat t. a driven shaft, amagnetic clutch between the two shafts, and a source of electricalcurrent, the improvement of circuit means for momentarily energizing themagnetic clutch for transmitting power from the driving. shaft to thedriven shaft, said improvement comprising circuit connection. means forconnecting. the magnetic clutch to the source of electric current, andan electrical tim-,

ing circuit including a grid-controlled tube and a capacitor forgoverning the circuit connection means, said circuit connection meanscontrolling the electrical timing circuit.

3. In a control system having a driving shaft, a driven shaft, amagnetic clutch between the two shafts, and a source of electricalcurrent, the immovement of circuit means for momentarily energizing themagnetic clutch for transmitting power from the driving shaft to thedriven shaft. said improvement comprising circuit connection means forconnecting the magnetic clutch to the source of electric current, anelectrical timing circuit including a grid-controlled tube and acapacitor for governing the circuit connection means, said circuitconnection means controllin the electrical timing circuit, and means forarresting the rotation of the driving shaft upon failure of theelectrical timing circuit.

4.. In a control system having a movable work table, a movable tooldevice, and a source of electrical current, the improvement of circuitmeans for moving the tool device with respect to the work table, saidcircuit means comprising, driving means for the tool device, magneticclutch means for governing the driving means, circuit connection meansfor connecting the magnetic clutch to the source of electric current, anelectrical timing circuit for governing the circuit connection means,said circuit connection means controlling the electric timing circuit,and means responsive to the movements of the work table for governingthe electrical timing circuit.

5. In a control system having a movable work table, a movable tooldevice, and a source of electrical current, the improvement of circuitmeans for moving the tool device with respect to the work table, saidcircuit means comprising, driving means for the tool device, magneticclutch means for governing the driving means, circuit connection meansfor connecting the magnetic clutch to the source of electric current, anelectrical timing circuit including a grid-controlled tube and acapacitor for governing the circuit connection means, and meansresponsive to the movements of the work table for governing theelectrical timing circuit.

6. In a control system having a movable work table, a movable tooldevice, and a source of electric current, the improvement of circuitmeans for moving the tool device with respect to the Work table, saidcircuit means comprising, electric means for controlling the movementsof the movable tool device, circuit connection means for connecting theelectric means to the source of electric current, an electrical timingcircuit including a grid-controlled tube and a capacitor for governingthe circuit connection means, and means responsive to the movements ofthe work table for governing the electrical timing circuit.

'7. In a control system having a movable wort; table, a movable tooldevice, and a source of electric current, the improvement of circuitmeans for moving the tool device with respect to the work table, saidcircuit means comprising, electric means for controlling the movementsof the movw able tool device, circuit connection means for connectingthe electric means to the source of electric current, an electricaltiming circuit for governing the circuit connection means, meansresponsive to the movements of the work table for governing theelectrical timing circuit, and means for arresting the movements of thetool device upon failure of the electrical timing circuit.

8. In a control system having a movable work table, a movable tooldevice, and a source of electric current, the improvement of circuitmeans for moving the tool device with respect to the work table, saidcircuit means comprising, an electric motor for driving the tool device,a magnetic clutch between the electric motor and the tool device, meansfor energizin the electric motor, circuit connection means forconnecting the magnetic clutch to the source of electric current, anelectrical timing circuit for governing the circuit connection means,and means responsive to the movements of the work table for governingthe electrical timing circuit.

9. In a control system having a movable work table, a movable tooldevice, and a source of electric current, the improvement of circuitmeans for moving the tool device with respect to the work table, saidcircuit means comprising, an electric motor for driving the tool device,a magnetic clutch between the electric motor and the tool device, meansfor energizing the electric motor, circuit connection means forconnecting the magnetic clutch to the source of electric current, anelectrical timing circuit for governing the circuit connection means,means responsive to the movements of the work table for governing theelectrical timing circuit, and means for tie-energizing the electricmotor upon failure of the electrical timing circuit.

10. In a control system having a movable work table, a movable tooldevice, and a source of electric current, the improvement of circuitmeans for moving the tool device with respect to the work table, saidcircuit means comprising, an electric motor for driving the tool device,a magnetic clutch between the electric motor and the tool device, meansfor energizing the electric motor, circuit connection means forconnecting the magnetic clutch to the source of electric current, anelectrical timing circuit for governing the circuit connection means,said circuit connection means controlling the electrical timing circuit,means responsive to the movements of the work table for governing theelectrical timing circuit, and means for de-energizing the electricmotor upon failure of the electrical timing circuit.

GEORGE H. PARDEY. CORNELIUS L. JOHNSON.

